Spray Drying Handbook

Abstract

Drying, with particular reference to solid materials or the single-step production of solid materials from solutions, slurries or suspensions, generally, is understood to concern the removal of moisture by thermal means and can occur only when the moisture's vapor pressure is greater than its partial pressure in the surrounding environment. If these two pressures are identical, no amount of energy application will promote drying.The purpose of supplying energy is (i) to raise the temperature of the moisture so that its vapor pressure is above its ambient partial pressure, and (ii) to provide energy for vaporization and any sensible-heat requirement of the generated vapor. The minimum temperature to which any material must be raised depends on the moisture's ambient partial pressure and the maximum temperature is limited by the material's susceptibility to adverse thermal effects. In a broad sense, drying may be viewed as a materials-handling problem, with primary selections of a dryer ordinarily based on the physical nature of the feedstock, Downloaded by [New York University] at 03:56 08 January 2015 420 BOOK REVIEW and the final choice often based on the desired physical form of the dried material. Operation mode and drying conditions usually are dictated by required product properties. Few feedstocks exhibit identical drying characteristics. From the viewpoint of dryer performance for a given system and set of operation conditions, the rate of drying increases as area per unit volume of feedstock available for heat and mass transfer is increased. Advantage is taken of this feature in the drying of thin films and small particles with the drying of liquid particles in the form of sprays enjoying extensive and varied application in the process industries. Although simple in concept, spray drying involves four distinct processing steps whose potential for interaction is great and whose kinetics can differ markedly. The first comprehensive review of spray drying was authored by W.R. Marshall, Jr., under the title "Atomization and Spray Drying" (AIChE Monograph, Ser. No. 2, 1954). During the following years, a number of similar works appeared--particularly in languages other than English. In 1972 the first edition of the "Handbook of Spray Drying" was published under the title Spray Drying. In 1976 a slightly altered and amended second edition was released. With the publication of the third edition in 1979, there were substantial changes in content and manner of presentation. In addition, the title was changed to its present form. The latest edition contains no major revisions. This book is authored by an industrialist having well over 22 years' experience with one of the world's major suppliers of spraydryers. As might be expected, the subject matter is generally treated more from the perspective of the manufacturer than the user and more from the viewpoint of the equipment operation than product production. The text is written Downloaded by [New York University] at 03:56 08 January 2015 BOOK REVIEW 421 essentially...

Spray-drying of fruit and vegetable juices: Effect of drying conditions on the product yield and physical properties

“…Dentro de las técnicas de secado aplicadas en alimentos, se resaltan las siguientes: secado conectivo con aire, secado al vacío, liofilización, secado por atomización o aspersión (SA), secado en ventanas refractivas, entre otros. Dentro de las técnicas de secado, el secado por atomización es aplicado para producir polvos de frutas; se utiliza ampliamente en la industria láctea, bebidas de chocolate, entre otros (Johansen Crosby, 1989).…”

“…La atomización es el proceso de reducción del tamaño de partícula de una corriente líquida en gotas con un diámetro entre 20 -180 m, y tiene por objetivo incrementar el área de contacto entre la corriente líquida y la corriente gaseosa para el desarrollo de los procesos simultáneos de transferencia de calor y masa. La elección de la configuración del atomizador depende de la naturaleza y la viscosidad de la alimentación y las características deseadas del producto seco (Johansen Crosby, 1989).…”